This invention relates to novel tetraphosphonic acid compounds, intermediate tetraphosphonate ester compounds and processes for their production. Such compounds are believed to be unknown in the literature and likewise the processes for their production are unknown. More specifically, the present invention includes ethylene tetraphosphonic acid, intermediate octaalkyl ethanetetraphosphonate esters and certain other intermediates in the process for production of the tetraphosphonic acid composition. The process of the present invention includes an electrolytic coupling.
Although electrochemical coupling of radicals formed by anodic oxidation is known, previous processes have problems with selectivity, efficiency and expense. A Review of the Oxidative Electrochemical Coupling of Organic Anions, Edited by Baizer Organic Electrochemistry, Marcelle Decker, Inc., New York, N.Y., p. 718 et seq (1973), shows that acetonitrile is a preferred solvent when used with platinum electrodes. U.S. Pat. No. 4,434,032, to Baldwin et al, teaches an electrochemical coupling to produce a symmetrical alkanediol by first making a bis ether from a haloalkanol, then electrochemically coupling the bis ether by removal of the halo group, and finally de-etherifying to produce the desired alkanediol.
The dealkylation of phosphonic acid dialkyl esters by reaction with iodotrimethylsilane to produce the corresponding bistrimethylsilyl esters and the subsequent hydrolysis of these products to the parent phosphonic acids under mild conditions is described by Blackburn et al, Journal of the Chemical Society, Chemical Communications, 1978, pages 870-871, and J. C. S. Perkin I, 1980, pages 1150-1153. In a similar teaching, Morita et al, Journal of the Chemical Society, Chemical Communications, 1978, pages 874-875, teach the use of chlorotrimethylsilane and sodium iodide as a dealkylation agent for carboxylic acid esters to give the silyl derivatives, followed by simple conversion of the silyl derivatives to the corresponding carboxylic acids and phenols. Morita et al also teach a similar reaction of dialkyl phosphonates with chlorotrimethylsilane in the presence of sodium-iodide, followed by hydrolysis under mild conditions at Tetrahedron Letters, No. 28, 1978, pages 2523-2526.